MAX16039 Maxim Integrated Products, MAX16039 Datasheet - Page 15

• Manufacturer Part Number: MAX16039
• Description: (MAX16033 - MAX16040) Low-Power Battery Backup Circuits
• Manufacturer: Maxim Integrated Products

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Connect the circuit as shown in Figure 9 to use the
power-fail comparator to monitor a negative supply rail.
PFO stays low when V- is good. When V- rises to cause
PFI to be above +1.235V, PFO goes high. Ensure V
comes up before the negative supply.
The MAX16033–MAX16040 are relatively immune to
short-duration, negative-going V
Resetting the µP when V
glitches is not usually desired.
The Typical Operating Characteristics section contains
a Maximum Transient Duration vs. Reset Threshold
Overdrive graph. The graph shows the maximum pulse
width of a negative-going V
trigger a reset pulse. As the amplitude of the transient
increases (i.e., goes further below the reset threshold
voltage), the maximum allowable pulse width decreas-
es. Typically, a V
the reset threshold and lasts for 25µs does not trigger a
reset pulse.
A 0.1µF bypass capacitor mounted close to V
vides additional transient immunity.
Negative-Going V
CC
______________________________________________________________________________________
transient that goes 100mV below
Monitoring a Negative Voltage
CC
CC
experiences only small
transient that would not
Circuits in Small µDFN Packages
CC
CC
Transients
transients.
CC
Low-Power Battery Backup
pro-
CC
Figure 9. Monitoring a Negative Voltage
V
V
V
V
TRIP
L
PFT
PFH
PFO
=
=
R
=
=
R1
R2
2
1 235
12
⎡
⎢
⎣
R
V-
.
(
V
2
mV
⎡
⎢
⎣
PFT
(
V
V
PFT
)
PFI
⎛
⎜
⎝
R
1
V
+
1
L
MAX16033–
MAX16040
3.0V OR 3.3V
+
V
GND
PFH
V
V
CC
R
TRIP
1
2
)
⎞
⎟ −
⎠
⎛
⎜
⎝
R
PFO
1
1
V
R
0V
+
CC
1
R
1
⎤
⎥
⎦
2
⎞
⎟ −
⎠
V
V-
R
CC
1
⎤
⎥
⎦
15